1. Field of Invention
This invention relates to a method and apparatus for projecting information on a chart of a chart recorder; and more particularly, to an improvement thereof wherein the information is projected on to a rear surface of the chart and then read from the front surface thereof.
2. Description of the Prior Art
Chart recorders, such as those using circular charts, are widely used for recording and monitoring measurement data because of their economy, compactness and lightness of weight. Except for the chart paper itself, the front of the chart recorder is usually completely concealed by a cover. But, in point of fact, only a small part of the recorder front is actually covered since most of the front is taken up by the chart. Recently, microprocessor based digital technology has been incorporated into chart recorders, thereby enabling the chart recorders to handle a large amount and variety of information in addition to the recorded signals. Thus, it has become necessary to display on the chart of the recorder the foregoing information and other digital information necessary to configure various parameters for digital processing.
To equip the recorder with an additional digital display device however would use up added front surface space. Since the front surface area of the recorder is currently so limited on conventional recorders, adding any further display devices is not entirely feasible. Adding a separate information indicating mechanism would require an increase in the total front viewing area of the recorder and hence increase the total cost. This would detract from the utility of the chart recorders, which are widely used because of their economy, compactness and lightness of weight.
Moreover, adding such separate indicating mechanism would go counter to the current trend in technical development, wherein every effort is being made to reduce the size thereof and to increase the amount of information derivable from a smaller sized area. The display area of chart recorders used with the developing instrumentation systems is thus also becoming smaller and smaller while the information being displayed is increasing.
Accordingly, an object of the invention is to overcome the aforementioned and other deficiencies and disadvantages of the prior art.
The aforementioned and other objects are attained by the invention which encompasses a device for indicating information using light emitting devices disposed on the inside or back surface (the outside or front surface of the chart being the viewing surface) of a chart on which measurement signals are recorded on the front or viewing surface thereof. The light beams from the devices are transmitted from the back surface through the chart and appear on the front surface of the chart, thereby enabling various types of information to be indicated on the front surface of the chart.
Hence, advantageously, the invention enhances the functionality of a compact chart recorder having a small display area, by (1) projecting different types of information onto the rear surface of the chart on which measured information is recorded on a front surface thereof, (2) enabling the information to be read from the front surface of the chart after being transmitted from the rear surface and through the chart; and (3) enabling data values and parameters to be viewed and configured easily without sacrificing any of the other features of conventional chart recorders. In this manner while maintaining the advantages of conventional chart recorders, the invention also provides added data for viewing from the front of the chart without requiring added separate indicating devices.